1. Field of the Invention
This invention relates to improvements in wound coils with integral cooling passages, and more particularly in magnetic repulsion drive coil for a flex punch to a drive coil with improved current distribution and improved heat transfer characteristics.
2. Description of the Prior Art
The invention is disclosed herein with reference to its specific preferred embodiment of a tape wound coil for a flex punch. However, as also disclosed and claimed, the basic technology has additional applications.
Flex punches, using a magnetic repulsion drive coil are described in U.S. Pat. Nos. 4,872,381 and 4,821,614, assigned to the assignee of this application and incorporated herein by reference.
A drive coil for a magnetic repulsion flex punch is described in IBM Information Disclosure Bulletin Vol. 33, No. 4, September 1990.
As will be appreciated by those skilled in the art, magnetic repulsion flex punch technology is used to punch via openings in so-called green sheets used in making multi-layer ceramic substrates. As described in greater detail in the aforereferenced IBM Technical Disclosure Bulletin, a drive coil for such magnetic repulsion punches can be advantageously made from a thin copper strip wound into a tight spiral around a central conductive rod. A thin insulating coating covers one surface of the copper strip and the strip is wound with the uninsulated surface outwardly facing. Another conductive post is attached to the coil at its outer peripheral surface.
While generally satisfactory, the rate at which heat can be removed from prior art magnetic repulsion drive coils is limited and, this in turn, limits the frequency at which the punch can operate.